Delivery of a drug, hormone, protein, or other medically active agent into a patient faces a number of challenges. The medically active agent has to be delivered into the patient. Two such ways are ingestion and injection. With ingestion the drug may have to pass through a patient's digestive system before reaching the bloodstream or targeted area for treatment. Injection may allow the medically active agent to reach the bloodstream or targeted area for treatment quickly or directly, but injection may be inconvenient or painful for the patient. Once in the body, the concentration of the medically active agent as a function of time may vary depending on the type of medically active agent, the attachment of different functional groups or molecules on the medically active agent, the encapsulation of the medically active agent, or other factors. If the concentration of the medically active agent decreases below a threshold, the medically active agent may need to be administered once again. Many medically active agents have to be administered frequently, including several times a day. A more frequent administration schedule may increase the inconvenience to the patient, may decrease the compliance rate by patients, and may lead to less than optimal outcomes for the patient. If the medically active agent is administered by injection, another injection increases the frequency of pain, the risk of infection, and the probability of an immune response in the patient. Thus, a need for medically active agents that have superior concentration profiles in the patient exists. The methods and compositions described herein provide solutions to these and other needs.